AND RATIO OF THEIR ATOMIC WKKIIITS. 



63 



barometer, were used. In tliis ease, the two readiugs of level were made on 

 the same scale, lu'cause the two levels of the mercMii) were in the same 

 perpendicular. 



Tlie time dining wliicli occasional readings of pressure were miide v;nied from 

 an h<iur to three oi' four Imurs. 



lt». SKCOND J[KTIIol>. 01!SKKVATn)NS AND RESULTS. 



As iu the case of the third series of determinations of the density of oxygen, 

 there was no room for the exercise of judgment in combining the observations. 

 The expei'iments are also affected with a source of constant eri'or, as will be 

 mentioned in more detail ; so that there is the less reason for giving more than the 

 pressures and weights observed, together \vith the density reduced to the sea level 

 at latitude 45°, by the formula 



If we increase the mean by one thirty-thousandth,* we get 



D = O.OS9970 gr, ± 0.000011. 



11. REMARK ON THE RESULTS OF THE FIRST AND SECOND SERIES. 



The degree of precision attained in weighing so light a gas as hydrogen in 

 either series of experiments was of course not very great, and the two mean 

 values obtained agree more closely than would be expected. Perhaps they are 

 sufficient to show that the method of weighing hydrogen in globes exhausted with 



* See note, page 28. 



